Hmmm....well, I can think of countless simpering female anime characters...so, let's stick to Supernatural.
I'm going to go ahead and say Meg.
Now, hear me out, because I know for some reason people love Meg... I find her annoying because I'm supposed to. She's a villain, so I have much the same reaction to her as Dean and Sam do whenever she shows up.
It also annoys me that we don't know her name. She's Meg because that's the first body they met her in. When she possesses Sam, Dean asks her who she is and she says "I go by many names - right now, I'm Sam" - which is all well and good, but every other demon had a constant name that was independent of the body they were in, and it sort of annoys me that we don't know hers.